Abstract: An error of stored data is detected with high accuracy. Data (e.g., a remainder in a CRC) used for detecting an error is stored in a memory in which an error is unlikely to occur. Specifically, the following semiconductor device is used: a memory element including a plurality of transistors, a capacitor, and a data storage portion is provided in a matrix; the data storage portion includes one of a source and a drain of one of the plurality of transistors, a gate of another one of the plurality of transistors, and one electrode of the capacitor; a semiconductor layer including a channel of the transistor, the one of the source and the drain of which is connected to the data storage portion, has a band gap of 2.8 eV or more, or 3.2 eV or more; and the data storage portion stores data for detecting an error.